Meiotic Research Articles

Novel Populations of Mycobacterium smegmatis Under Hypoxia and Starvation: Some Insights on Cell Viability and Morphological Changes

The general features of the shift to a dormant state in mycobacterial species include several phenotypic changes, reduced metabolic activities, and increased resistance to host and environmental stress conditions. In this study, we aimed to provide novel insights into the viability state and morphological changes in dormant M. smegmatis that contribute to its long-term survival under starvation or hypoxia. To this end, we conducted assays to evaluate cell viability, morphological changes and gene expression. During starvation, M. smegmatis exhibited a reduction in cell length, the presence of viable but non-culturable (VBNC) cells and the formation of anucleated small cells, potentially due to a phenomenon known as reductive cell division. Under hypoxia, a novel population of pleomorphic mycobacteria with a rough surface before the cells reached nonreplicating persistence 1 (NRP1) was identified. This population exhibited VBNC-like behaviour, with a loss of cell wall rigidity and the presence of lipid-body-like structures. Based on dosR and hspX expression, we suggest that M. smegmatis encounters reductive stress conditions during starvation, while lipid storage may induce oxidative stress during hypoxia. These insights into the heterogeneous populations presented here could offer valuable opportunities for developing new therapeutic strategies to control dormant mycobacterial populations.

Inter-reader agreement of the BI-RADS CEM lexicon.

The purpose of this study was to assess the inter-reader agreement of the breast imaging reporting and data system (BI-RADS) contrast-enhanced mammography (CEM) lexicon. In this IRB-approved, single-center, retrospective study, three breast radiologists, each with different levels of experience, reviewed 462 lesions in 421 routine clinical CEM according to the fifth edition of the BI-RADS lexicon for mammography and to the first version of the BI-RADS lexicon for CEM. Readers were blinded to patient outcomes and evaluated breast and lesion features on low-energy (LE) images (breast density, type of lesion, associated architectural distortion), lesion features on recombined (RC) images (type of enhancement, characteristic of mass enhancement, non-mass enhancement or enhancing asymmetry), and provided a final BI-RADS assessment. The inter-reader agreement was calculated for each evaluated feature using Fleiss' kappa coefficient. Sensitivity and specificity were calculated. The inter-reader agreement was moderate to substantial for breast density (ĸ = 0.569), type of lesion on LE images (ĸ = 0.654), and type of enhancement (ĸ = 0.664). There was a moderate to substantial agreement on CEM mass enhancement descriptors. The agreement was fair to moderate for non-mass enhancement and enhancing asymmetry descriptors. Inter-reader agreement for LE and LE with RC BI-RADS assessment was moderate (ĸ = 0.421) and fair (ĸ = 0.364). Diagnostic performance was good and comparable for all readers. Inter-reader agreement of the CEM lexicon was moderate to substantial for most features. There was a low agreement for some RC descriptors, such as non-mass enhancement and enhancing asymmetry, and BI-RADS assessment, but this did not impact the diagnostic performance. Question Data on the reproducibility and inter-reader agreement for the first version of the BI-RADS lexicon dedicated to CEM are missing. Finding The inter-reader agreement for the lexicon was overall substantial to moderate, but it was lower for the descriptors for non-mass enhancement and enhancing asymmetry. Clinical relevance A common lexicon simplifies communication between specialists in clinical practice. The good inter-reader agreement confirms the effectiveness of the CEM-BIRADS in ensuring consistent communication. Detailed definitions of some descriptors (non-mass, enhancing asymmetry) are needed to ensure higher agreements.

Изучение потребности сортов плодовых культур в температурном режиме прохождения фаз их развития (на примере сортов груши)

Abstract. The ontogeny of fruit crops and varieties is composed of individual morphological cycles, each of which has its own requirements of the temperature regime. One of the most important cycles in the formation of flower buds is the development of archesporial tissue in their anthers during winter-spring development, which, in turn, consists of several stages (phases I, II, III). They require a certain amount of active temperatures for their passage. Their deficiency (or excess) can lead to a suspension of ontogeny or even death of flower buds.This paper presents a scientific approach to determining the boundaries of active temperatures necessary for the passage of ontogenesis phases in the buds of pear varieties in the winter-spring and summer periods. Until now, the calculation of the sums of average temperatures received by plants is usually carried out above +5 ºС (active) and above +10 ºС (effective), which does not meet modern requirements for studying the production process and needs to be adjusted. Objective indicators of active temperature limits for pear varieties in specific phases of winter-spring and summer development have been determined. For the Williams variety, the optimal temperature for going through the “budbreak” phase (reduction division) is +6 °C. For varieties Leven, Kieffer – +5 °С. For the Lyubimitsa Klappa variety – +7 °C. It turned out to have the highest active temperature limit. Consequently, this variety has increased thermophilicity compared to the other three varieties studied.The work reveals the possibility of a more correct study of the needs of specific varieties in the amount of temperatures required to pass through each phase of ontogenesis. Its results are important for revealing the mechanism of interaction “genotype-temperature environmental conditions” when controlling the production process of fruit crops and their varieties in various growing environmental conditions in order to increase yield and for further breeding. Key words: variety, pear, temperature regime, production process

Microtubules and actin filaments direct nuclear movement during the polarisation of Marchantia spore cells.

The multicellular haploid stage of land plants develops from a single haploid cell produced by meiosis - the spore. Starting from a non-polar state, these spores develop polarity, divide asymmetrically and establish the first axis of symmetry. Here, we show that the nucleus migrates from the cell centroid to the basal pole during polarisation of the Marchantia polymorpha spore cell. A microtubule organising centre on the leading edge of the nucleus initiates a microtubule array between the nuclear surface and the cortex at the basal pole. Simultaneously, cortical microtubules disappear from the apical hemisphere but persist in the basal hemisphere. This is accompanied by the formation a dense network of fine actin filaments between the nucleus and the basal pole cortex. Experimental depolymerisation of either microtubules or actin filaments disrupts cellular asymmetry. These data demonstrate that the cytoskeleton reorganises during spore polarisation and controls the directed migration of the nucleus to the basal pole. The presence of the nucleus at the basal pole provides the cellular asymmetry for the asymmetric cell division that establishes the apical-basal axis of the plant.

Cohesin ring gates are specialized for meiotic cell division.

Cohesin is a ring complex closed with SMC-1, SMC-3, and a kleisin subunit, mediating sister chromatid cohesion in mitosis and meiosis. Kleisin N- and C-terminal domains interact with SMC-3 and SMC-1, forming two distinct cohesin gates. Whether these gates are specialized for mitosis and meiosis remains elusive. Here, we create Caenorhabditis elegans mutants that express chimeric proteins swapping N- and C-terminal domains between different kleisins to investigate how these gates are specialized for different cell division programs. Replacing the meiotic REC-8 N-terminus with that of a cell division-unrelated kleisin COH-1 or the mitotic kleisin SCC-1 disrupts inter-sister chromatid cohesion and causes severe meiotic defects. Swapping the REC-8 C-terminus with that of COH-1 or SCC-1 largely retains the meiotic functions of REC-8 but causes age-related chromosome abnormalities. A specialized C-terminus is also required for the functions of SCC-1. Furthermore, point mutations in REC-8 C-terminus cause severe meiotic defects without impairing SMC-1-kleisin interaction, suggesting an integrated SMC-1-kleisin gate. These findings suggest the requirements for specialized cohesin gates in different biological processes.

Length-sensitive partitioning of Caenorhabditis elegans meiotic chromosomes responds to proximity and number of crossover sites

Sensing and control of size are critical for cellular function and survival. A striking example of size sensing occurs during meiosis in the nematode Caenorhabditis elegans. C.elegans chromosomes compare the lengths of the two chromosome "arms" demarcated by the position of their single off-center crossover, and they differentially modify these arms to ensure that sister chromatid cohesion is lost specifically on the shorter arm in the first meiotic division, while the longer arm maintains cohesion until the second division. While many of the downstream steps leading to cohesion loss have been characterized, the length-sensing process itself remains poorly understood. Here, we have used cytological visualization of short and long chromosome arms, combined with quantitative microscopy, live imaging, and simulations, to investigate the principles underlying length-sensitive chromosome partitioning. By quantitatively analyzing short-arm designation patterns on fusion chromosomes carrying multiple crossovers, we develop a model in which a short-arm-determining factor originates at crossover designation sites, diffuses within the synaptonemal complex, and accumulates within crossover-bounded chromosome segments. We demonstrate experimental support for a critical assumption of this model: that crossovers act as boundaries to diffusion within the synaptonemal complex. Further, we develop a discrete simulation based on our results that recapitulates a wide variety of observed partitioning outcomes in both wild-type and previously reported mutants. Our results suggest that the concentration of a diffusible factor is used as a proxy for chromosome length, enabling the correct designation of short and long arms and proper segregation of chromosomes.

C19MC drives nucleolar invasion of mitochondria and meiotic nuclear division in human cancers

C19MC drives nucleolar invasion of mitochondria and meiotic nuclear division in human cancers

DNA Damage, Cell Death, and Alteration of Cell Proliferation Insights Caused by Copper Oxide Nanoparticles Using a Plant-Based Model.

The speedy growth of copper oxide nanoparticle (CuO NP) manufacturing due to their wide application in industries has caused concerns due to their increased discharge into the environment from both purposeful and accidental sources. Their presence at an elevated concentration in the environment can cause potential hazards to the plant kingdom, specifically to staple food crops. However, limited research is available to determine the consequences of CuO NPs. The present study aimed to assess the morphological and cytological changes induced by CuO NPs on Pisum sativum L., a key staple food crop. Seeds of Pisum sativum were exposed to various concentrations of CuO NPs (0, 25, 50, 75, 100, and 125 ppm) for 2 h, and their effects on seed germination (SG), radicle length (RL), cell proliferation kinetics (CPK), mitotic index (MI), cell death (CD), micronucleus frequency (MNF), and chromosomal aberration frequency (CAF) were studied. The results indicate a significant reduction in SG, RL, CPK, and MI and a significant dose-dependent increase in CD, MNF, and CAF. CuO NP treatment has led to abnormal meiotic cell division, increased incidence of micronucleus frequency, and chromosomal aberration frequency. Additionally, the CuO NP-treated groups showed an increase in the percentage of aberrant meiotic cells such as laggard (LG), double bridge (DB), stickiness (STC), clumped nuclei (CNi), precocious separation (PS), single bridge (SB), and secondary association (SA). CuO NP treatment led to reductions in SG as follows: 55% at 24 h, 60.10% at 48 h, and 65% at 72 h; reductions in RL as follows: 0.55 ± 0.021 cm at 24 h, 0.67 ± 0.01 cm at 48 h, and 0.99 ± 0.02 cm at 72 h; reductions in CPK as follows: 34.98% at prophase, 7.90% at metaphase, 3.5% at anaphase, and 0.97% at telophase. It also led to a 57.45% increase in CD, a 39.87% reduction in MI, and a 60.77% increase in MNF at a higher concentration of 125 ppm. The findings of this study clearly show that CuO NPs have a genotoxic effect on the food crop plant Pisum sativum.

Quantitative proteomics and phosphoproteomics profiling of meiotic divisions in the fission yeast Schizosaccharomyces pombe

In eukaryotes, chromosomal DNA is equally distributed to daughter cells during mitosis, whereas the number of chromosomes is halved during meiosis. Despite considerable progress in understanding the molecular mechanisms that regulate mitosis, there is currently a lack of complete understanding of the molecular mechanisms regulating meiosis. Here, we took advantage of the fission yeast Schizosaccharomyces pombe, for which highly synchronous meiosis can be induced, and performed quantitative proteomics and phosphoproteomics analyses to track changes in protein expression and phosphorylation during meiotic divisions. We compared the proteomes and phosphoproteomes of exponentially growing mitotic cells with cells harvested around meiosis I, or meiosis II in strains bearing either the temperature-sensitive pat1-114 allele or conditional ATP analog-sensitive pat1-as2 allele of the Pat1 kinase. Comparing pat1-114 with pat1-as2 also allowed us to investigate the impact of elevated temperature (25 °C versus 34 °C) on meiosis, an issue that sexually reproducing organisms face due to climate change. Using TMTpro 18plex labeling and phosphopeptide enrichment strategies, we performed quantification of a total of 4673 proteins and 7172 phosphosites in S. pombe. We found that the protein level of 2680 proteins and the rate of phosphorylation of 4005 phosphosites significantly changed during progression of S. pombe cells through meiosis. The proteins exhibiting changes in expression and phosphorylation during meiotic divisions were represented mainly by those involved in the meiotic cell cycle, meiotic recombination, meiotic nuclear division, meiosis I, centromere clustering, microtubule cytoskeleton organization, ascospore formation, organonitrogen compound biosynthetic process, carboxylic acid metabolic process, gene expression, and ncRNA processing, among others. In summary, our findings provide global overview of changes in the levels and phosphorylation of proteins during progression of S. pombe cells through meiosis at normal and elevated temperatures, laying the groundwork for further elucidation of the functions and importance of specific proteins and their phosphorylation in regulating meiotic divisions in this yeast.

Meiosis in plants: from Understanding to Manipulation

Meiosis is an indispensable process in sexual reproduction, involving the recombination of genetic information and the production of haploid gamete cells through the segregation of sister chromatids. In crop breeding, elucidating the molecular mechanisms of meiosis is fundamental for manipulating recombination frequency and distribution, as well as for generating polyploid plants. In this review, we summarize current knowledge on the processes and genes involved in genetic recombination during Meiosis I, and the regulatory mechanisms of the second meiotic division during Meiosis II. Furthermore, we have outlined the breeding innovations achieved through the manipulation of meiosis, including the enhancement of genetic recombination frequency, alteration of recombination distribution, construction of artificial apomixis systems, and implementation of autopolyploid progressive heterosis (APH). This knowledge forms the cornerstone for further crop breeding applications, ultimately contributing to the optimization of crop yield and quality.

Abnormal expression of LiASY1 and LiDMC1 is the main cause of sterility in F1 hybrids developed from Lagerstroemia speciosa and Lagerstroemia indica ‘Ebony Embers’

Lagerstroemia × ‘Xiaoxiang Huaxiu’ (an F1 hybrid of Lagerstroemia speciosa and Lagerstroemia indica ‘Ebony Embers’) exhibits significant sterility. Cytological studies have revealed numerous abnormal chromosomal behaviors during the meiotic division of pollen mother cells in L. × ‘Xiaoxiang Huaxiu’. Transcriptome sequencing identified that LiDMC1 and LiASY1 were expressed at very low levels in ‘Xiaoxiang Huaxiu’. To further verify whether the abnormal expression of LiDMC1 and LiASY1 was the fundamental cause of sterility in ‘Xiaoxiang Huaxiu’, we cloned the full-length gene sequences of LiDMC1 and LiASY1 from ‘Ebony Embers’. Using VIGS (virus-induced gene silencing) technology, pTRV1 and pTRV2 gene silencing vectors were employed to silence LiDMC1 and LiASY1 in the paternal parent ‘Ebony Embers’. The results indicated that in the double-silenced lines of ‘Ebony Embers’, the cytoplasm sizes of different tetrads during the tetrad stage varied significantly. There was a notable proportion of polyads, binucleate cells with micronuclei, and pentads. Additionally, pollen diameter varied significantly, closely resembling the sterility observed in ‘Xiaoxiang Huaxiu’. Pollen viability in the double-silenced ‘Ebony Embers’ decreased by 22.8%. This study demonstrates that the low expression of LiDMC1 and LiASY1 leads to abnormal microspore development in ‘Ebony Embers’, and their low expression is the cause of sterility in ‘Xiaoxiang Huaxiu’.

Histological Study of Development Structure of Testis and Epididymis in Gazelle Gazelle Subgutturosa

Objective: The aim of this study for focused the light on the development structure of the testis of gazelle. Materials and Method: 10 healthy male gazelle were used to study the histology structure of testis (5 pre- Puberty and 5 post- Puberty). Results: The testis is surrounded by a thick, irregular connective tissue capsule. Each lobule of the testis is composed of seminiferous tubules and interstitial tissue, and trabecular and interlobular septa divide the lobules apart. Neighboring the seminiferous tubules are Sertoli cells and spermatogenic cells. From spermatogenic cells, spermatozoa are produced. The first spermatogonia are small, spherical cells with black, spherical nuclei that reside on the basement membrane. Spermatogonia were earliest stages of the spermatogenic cells. Larger cells with frequently distinct chromatin are called primary spermatocytes. Secondary spermatocytes are rare because of their quick second meiotic division and the haploid spermatids that follow. Spermatids are round, pale-nucleated cells that are grouped close to the lumen of the seminiferous tubule. Prostatogenic cells outnumber Sertoli cells in the body. Oval or triangular in shape, the nucleus has a light coloration. In the connective tissue separating adjacent tubules, Leydig cells are present. Lines the epididymis are pseudostratified epithelium. Extensions of the cytoplasm into the lumen are called stereocilia. In different proportions, there is circular smooth muscle, and a connective tissue lamina propria supports the epithelium. The rete testis is connected to the ductus epididymidis by the efferent ductules, which are convolutions of tubules. Numerous valved veins were visible in the tunica albuginea, which covered the initial ascending portion of the epididymal head. Cuboidal epithelium was lining extratesticular rete testis. Three different cell types; migrating, basal, and columnar had epithelial membranes lining the efferent ductules. Many columnar, non-ciliated cells with many cytoplasmic vacuoles and tiny granules lined the epithelium of the first segment of the efferent ductules. Conclusion: In post-puberty age, the structure of the gazelle's testis exhibited a pattern resembling that of other ruminants; the seminiferous tubules contain adult sperm and a broad lumen.

Aligning genotyping and copy number data in single trophectoderm biopsies for aneuploidy prediction: uncovering incomplete concordance.

To what extent can genotype analysis aid in the classification of (mosaic) aneuploid embryos diagnosed through copy number analysis of a trophectoderm (TE) biopsy? In a small portion of embryos, genotype analysis revealed signatures of meiotic or uniform aneuploidy in those diagnosed with intermediate copy number changes, and signatures of presumed mitotic or putative mosaic aneuploidy in those diagnosed with full copy number changes. Comprehensive chromosome screening (CCS) for preimplantation genetic testing has provided valuable insights into the prevalence of (mosaic) chromosomal aneuploidy at the blastocyst stage. However, diagnosis of (mosaic) aneuploidy often relies solely on (intermediate) copy number analysis of a single TE biopsy. Integrating genotype information allows for independent assessment of the origin and degree of aneuploidy. Yet, studies aligning both datasets to predict (putative mosaic) aneuploidy in embryos remain scarce. A single TE biopsy was collected from 1560 embryos derived from 221 couples tested for a monogenic disorder (n = 218) or microdeletion-/microduplication syndrome (n = 3). TE samples were subjected to both copy number and genotyping analysis. Copy number and SNP genotyping analysis were conducted using GENType. Unbalanced chromosomal anomalies ≥10 Mb (or ≥20 Mb for copy number calls <50%) were classified by degree, based on low-range intermediate (LR, 30-50%), high-range intermediate (HR, 50-70%) or full (>70%) copy number changes. These categories were further subjected to genotyping analysis to ascertain the origin (and/or degree) of aneuploidy. For chromosomal gains, the meiotic division of origin (meiotic I/II versus non-meiotic or presumed mitotic) was established by studying the haplotypes. The level of monosomy (uniform versus putative mosaic) in the biopsy could be ascertained from the B-allele frequencies. For segmental aneuploidies, genotyping was restricted to deletions. Of 1479 analysed embryos, 24% (n = 356) exhibited a whole-chromosome aneuploidy, with 19% (n = 280) showing full copy number changes suggestive of uniform aneuploidy. Among 258 embryos further investigated by genotyping, 95% of trisomies with full copy number changes were identified to be of meiotic origin. For monosomies, a complete loss of heterozygosity (LOH) in the biopsy was observed in 97% of cases, yielding a 96% concordance rate at the embryo level (n = 248/258). Interestingly, 4% of embryos (n = 10/258) showed SNP signatures of non-meiotic gain or putative mosaic loss instead. Meanwhile, 5% of embryos (n = 76/1479) solely displayed HR (2.5%; n = 37) or LR (2.6%; n = 39) intermediate copy number changes, with an additional 2% showing both intermediate and full copy number changes. Among embryos with HR intermediate copy number changes where genotyping was feasible (n = 25/37), 92% (n = 23/25) showed SNP signatures consistent with putative mosaic aneuploidy. However, 8% (n = 2/25) exhibited evidence of meiotic trisomy (9%) or complete LOH in the biopsy (7%). In the LR intermediate group, 1 of 33 (3%) genotyped embryos displayed complete LOH. Furthermore, segmental aneuploidy was detected in 7% of embryos (n = 108/1479) (or 9% (n = 139) with added whole-chromosome aneuploidy). These errors were often (52%) characterized by intermediate copy number values, which closely aligned with genotyping data when examined (94-100%). N/A. The findings were based on single TE biopsies and the true extent of mosaicism was not validated through embryo dissection. Moreover, evidence of absence of a meiotic origin for a trisomy should not be construed as definitive proof of a mitotic error. Additionally, a genotyping diagnosis was not always attainable due to the absence of a recombination event necessary to discern between meiotic II and non-meiotic trisomy, or the unavailability of DNA from both parents. Interpreting (intermediate) copy number changes of a single TE biopsy alone as evidence for (mosaic) aneuploidy in the embryo remains suboptimal. Integrating genotype information alongside the copy number status could provide a more comprehensive assessment of the embryo's genetic makeup, within and beyond the single TE biopsy. By identifying meiotic aberrations, especially in presumed mosaic embryos, we underscore the potential value of genotyping analysis as a deselection tool, ultimately striving to reduce adverse clinical outcomes. L.D.W. was supported by the Research Foundation Flanders (FWO; 1S74621N). M.B., K.T., F.V.M., S.J., A.V.T., V.S., D.S., A.D., and S.S. are supported by Ghent University Hospital. B.M. was funded by Ghent University. The authors have no conflicts of interest.

Aurora B and Aurora C pools at two chromosomal regions collaboratively maintain chromosome alignment and prevent aneuploidy at the second meiotic division in mammalian oocytes.

Correct chromosome segregation is essential to preserve genetic integrity. The two protein kinases, Aurora B and its meiotic homolog Aurora C, regulate attachments between chromosomal kinetochores and microtubules, thereby contributing to the accuracy of the chromosome segregation process. Here we performed a detailed examination of the localization and activity of Aurora B/C kinases, their partner Incenp and the kinetochore target Hec1, during the second meiotic division in mouse oocytes. We found that a majority of Aurora B and C changed their localization from the outer kinetochore region of chromosomes at prometaphase II to an inner central region localized between sister centromeres at metaphase II. Depletion of the Aurora B/C pool at the inner central region using the haspin kinase inhibitor 5-iodotubercidin resulted in chromosome misalignments at the metaphase II stage. To further understand the role of the Aurora B/C pool at the central region, we examined the behaviour of single chromatids, that lack a central Aurora B/C pool but retain Aurora B/C at the outer kinetochores. We found that kinetochore-microtubule attachments at single chromatids were corrected at both prometaphase II and metaphase II stages, but that single chromatids compared to paired chromatids were more prone to misalignments following treatment of oocytes with the Aurora B/C inhibitory drugs AZD1152 and GSK1070916. We conclude that the Aurora B/C pool at the inner central region stabilizes chromosome alignment during metaphase II arrest, while Aurora B/C localized at the kinetochore assist in re-establishing chromosome positioning at the metaphase plate if alignment is lost. Collaboratively these two pools prevent missegregation and aneuploidy at the second meiotic division in mammalian oocytes.

The signal that stimulates mammalian embryo development.

Embryo development is stimulated by calcium (Ca2+) signals that are generated in the egg cytoplasm by the fertilizing sperm. Eggs are formed via oogenesis. They go through a cell division known as meiosis, during which their diploid chromosome number is halved and new genetic combinations are created by crossing over. During formation the eggs also acquire cellular components that are necessary to produce the Ca2+ signal and also, to support development of the newly formed embryo. Ionized calcium is a universal second messenger used by cells in a plethora of biological processes and the eggs develop a "toolkit", a set of molecules needed for signaling. Meiosis stops twice and these arrests are controlled by a complex interaction of regulatory proteins. The first meiotic arrest lasts until after puberty, when a luteinizing hormone surge stimulates meiotic resumption. The cell cycle proceeds to stop again in the middle of the second meiotic division, right before ovulation. The union of the female and male gametes takes place in the oviduct. Following gamete fusion, the sperm triggers the release of Ca2+ from the egg's intracellular stores which in mammals is followed by repetitive Ca2+ spikes known as Ca2+ oscillations in the cytosol that last for several hours. Downstream sensor proteins help decoding the signal and stimulate other molecules whose actions are required for proper development including those that help to prevent the fusion of additional sperm cells to the egg and those that assist in the release from the second meiotic arrest, completion of meiosis and entering the first mitotic cell division. Here I review the major steps of egg formation, discuss the signaling toolkit that is essential to generate the Ca2+ signal and describe the steps of the signal transduction mechanism that activates the egg's developmental program and turns it into an embryo.

Reserpine, a novel N6-methyladenosine regulator, reverses Lenvatinib resistance in hepatocellular carcinoma

BackgroundHepatocellular carcinoma (HCC) is an aggressive malignancy and a growing global health problem. Reserpine (Res), a plant-derived hypertension drug, has been reported to possess anti-tumor efficacy. However, the role and function of Res in N6-methyladenosine (m6A) regulation and Lenvatinib (Len) resistance in HCC have not been clarified. PurposeTo verify whether Res can be used as a natural small-molecule regulator of m6A to reverse Len resistance in HCC. MethodsDot blotting, Western blotting and m6A quantification were used to compare and analyze the differential expression of m6A and its methyltransferase METTL3. Western blotting, Real-Time PCR (RT-PCR), cellular thermal shift assay (CETSA) and molecular docking were used to explore the mechanism of interaction between Res and m6A. The effects of Res on the biological characteristics of Lenvatinib-resistant HCC cells were investigated through CCK-8, clone formation, and Transwell assays. Cell line-derived xenograft (CDX) and patient-derived xenograft (PDX) mouse models were used to assess the ability of Res to reverse Len resistance in vivo. MeRIP m6A sequencing, PATHWAY analysis and Western blotting were used to analyze the downstream signaling pathways and genes involved in Res-mediated reversal of Len resistance. ResultsLen resistance in HCC is related to the increased m6A level and the high expression of METTL3. Res affects the activity of METTL3 protein by binding to it, thereby downregulating the level of m6A. In vitro study showed that Res can sensitize HCC cells to the anti-tumor effects of Len treatment, including blocking proliferation, inhibiting migration, and inducing apoptosis. Len-resistant CDX and PDX models revealed that Res can reverse the resistant phenotype, with the tumor inhibition rates of 77.46 % and 62.1 %, respectively, when combined with Len treatment. Analysis of xenograft tissues showed that the combination of Res and Len down-regulates the m6A level, reduces proliferation biomarkers, and induces apoptosis, which is consistent with the in vitro data. Mechanistically, our preliminary results indicate that Res can up-regulate the SMAD3 level by down-regulating m6A in Len-resistant cells. ConclusionsReserpine, a small-molecule regulator of m6A, reverses Lenvatinib-resistant phenotypes, including proliferation, migration and anti-apoptosis, in vitro and in vivo by targeting SMAD3 and down-regulating the m6A level in HCC.

PELO regulates erythroid differentiation through interaction with MYC to upregulate KLF10.

Erythropoiesis is a multistep process of erythroid cell production that is controlled by multiple regulatory factors. Ribosome rescue factor PELO plays a crucial role in cell meiotic division and mice embryonic development. However, the function of PELO in erythroid differentiation remains unclear. Here, we showed that knockdown of PELO increased hemin-induced erythroid differentiation of K562 and HEL cells, exhibiting a higher number of benzidine-positive cells and increased mRNA levels of erythroid genes. PELO knockdown inhibited the proliferation and cell cycle progression and promoted apoptosis of K562 cells. Mechanistically, PELO could regulate the expression of KLF10 through interaction with MYC. Moreover, KLF10 knockdown also enhanced erythroid differentiation of K562 and HEL cells induced by hemin. Collectively, our results demonstrated that PELO regulates erythroid differentiation and increases KLF10 expression levels by interacting with MYC.

The role of DNA topoisomerase 1α (AtTOP1α) in regulating arabidopsis meiotic recombination and chromosome segregation.

Meiosis is a critical process in sexual reproduction, and errors during this cell division can significantly impact fertility. Successful meiosis relies on the coordinated action of numerous genes involved in DNA replication, strand breaks, and subsequent rejoining. DNA topoisomerase enzymes play a vital role by regulating DNA topology, alleviating tension during replication and transcription. To elucidate the specific function of DNA topoisomerase 1α ( ) in male reproductive development of Arabidopsis thaliana, we investigated meiotic cell division in Arabidopsis flower buds. Combining cytological and biochemical techniques, we aimed to reveal the novel contribution of to meiosis. Our results demonstrate that the absence of leads to aberrant chromatin behavior during meiotic division. Specifically, the top1α1 mutant displayed altered heterochromatin distribution and clustered centromere signals at early meiotic stages. Additionally, this mutant exhibited disruptions in the distribution of 45s rDNA signals and a reduced frequency of chiasma formation during metaphase I, a crucial stage for genetic exchange. Furthermore, the atm-2×top1α1 double mutant displayed even more severe meiotic defects, including incomplete synapsis, DNA fragmentation, and the presence of polyads. These observations collectively suggest that plays a critical role in ensuring accurate meiotic progression, promoting homologous chromosome crossover formation, and potentially functioning in a shared DNA repair pathway with ATAXIA TELANGIECTASIA MUTATED (ATM) in Arabidopsis microspore mother cells.

The deubiquitinase Usp7 in Drosophila melanogaster is required for synaptonemal complex maintenance.

Meiosis is a form of cell division that is essential to sexually reproducing organisms and is therefore highly regulated. Each event of meiosis must occur at the correct developmental stage to ensure that chromosomes are segregated properly during both meiotic divisions. One unique meiosis-specific structure that is tightly regulated in terms of timing of assembly and disassembly is the synaptonemal complex (SC). While the mechanism(s) for assembly and disassembly of the SC are poorly understood in Drosophila melanogaster, posttranslational modifications, including ubiquitination and phosphorylation, are known to play a role. Here, we identify a role for the deubiquitinase Usp7 in the maintenance of the SC in early prophase and show that its function in SC maintenance is independent of the meiotic recombination process. Using two usp7 shRNA constructs that result in different knockdown levels, we have shown that the presence of SC through early/mid-pachytene is critical for normal levels and placement of crossovers.

A conserved germline-specific Dsn1 alternative splice isoform supports oocyte and embryo development

The chromosome segregation and cell division programs associated with somatic mitosis and germline meiosis display dramatic differences such as kinetochore orientation, cohesin removal, or the presence of a gap phase.1,2,3,4,5,6 These changes in chromosome segregation require alterations to the established cell division machinery.5,6 It remains unclear what aspects of kinetochore function and its regulatory control differ between the mitotic and meiotic cell divisions to rewire these core processes. Alternative RNA splicing can generate distinct protein isoforms to allow for the differential control of cell processes across cell types. However, alternative splice isoforms that differentially modulate distinct cell division programs have remained elusive. Here, we demonstrate that mammalian germ cells express an alternative mRNA splice isoform for the kinetochore component, DSN1, a subunit of the MIS12 complex that links the centromeres to spindle microtubules during chromosome segregation. This germline DSN1 isoform bypasses the requirement for Aurora kinase phosphorylation for its centromere localization due to the absence of a key regulatory region allowing DSN1 to display persistent centromere localization. Expression of the germline DSN1 isoform in somatic cells results in constitutive kinetochore localization, chromosome segregation errors, and growth defects, providing an explanation for its tight cell-type-specific expression. Reciprocally, precisely eliminating expression of the germline-specific DSN1 splice isoform in mouse models disrupts oocyte maturation and early embryonic divisions coupled with a reduction in fertility. Together, this work identifies a germline-specific splice isoform for a chromosome segregation component and implicates its role in mammalian fertility.